The invention relates to a speed governor for a fuel injection pump for internal combustion engines. In a known speed governor of this kind (French laid-open patent application No. 20 54 116), a tension-loaded governor spring is provided which is coupled at one of its ends to a first support connected with an adjusting lever and at its other end to a second support connected with the governor lever. A part of one of the two supports protrudes coaxially into the center of the interior of the tensile spring and under the influence of the initial stress of the tension spring comes to rest on a part of the other support. The effective distance between the two support parts can be varied by means of a self-locking screw threaded into one of the two parts. In this manner, the initial stress of the spring is varied by varying the distance between the adjusting lever and the governor lever. A disadvantage of this arrangement, however, is that the outset position of the adjusting lever must be reset whenever the initial stress has to be adjusted to adapt it to the manufacturing tolerance of spring and connecting parts. In the known apparatus, an adjustment of the initial stress determines only the point of onset of speed regulation.
It has been found, however, that deviations in the degree of proportionality in mass production, that is the P-degree of the governor, occur because of manufacturing tolerances of the governor parts. Yet a very exact P-degree has to be adhered to particularly in the case of aggregate engines.
The degree of proportionality is the P-degree which indicates how high the rpm of a diesel engine during speed regulation increases from the rated rpm at full to the upper idling rpm. The P-degree is usually indicated in percent of the rpm increase up to the upper full-load rpm. The P degree has been set forth in the following publication:
BOSCH, "Technical Instruction, Fuel Injection Equipment for Diesel Engines (2) Governors for In-Line Pumps." Copyright Robert Bosch Gmbh (1975), Editor-in-Chief Ulrich Adler, Translation (1977) John T. Warner, Michael J. Scott, 1st edition September 1975, pages 8, 9, 13. A speed governor is also known from U.S. Pat. No. 3,942,498 granted Mar. 9, 1976. In this apparatus, the governor spring is embodied as a compression spring that is disposed coaxially with an actuation rod. The governor spring is supported on a spring plate on the actuation rod and on the side of this spring plate it is encompassed by a U-shaped bracket the ends of which are engaged by a further spring plate in a rotationally fixed manner with respect to a part of the U-shaped bracket; the further spring plate additionally acts as a guide means for the actuation rod. By means of the compression spring, the actuation rod is made to contact a part of the U-shaped bracket. With this apparatus, however, there is no way to compensate for manufacturing tolerances of the components of the governor spring assembly. Only the initial stress of the compression spring can be varied, by means of a spacer disc between the resting point of the one spring plate on the actuation rod and the spring plate.